57X99十57一99

Question

57X99十57一99

Answer 1

57X99+57-99
=57X99+57-99-1+1
=(57X99+57)-(99+1)+1
=57(99+1)-(99+1)+1
=(57-1)(99+1)+1
=56x100+1
=5600+1
=5601

Answer 2

57X99十57一99
=57×（99+1）-99
=57×100-99
=5700-99
=5601